How to incorporate op-amp clipping into a distortion circuit?

[Buran1997]

While breadboarding a simple LM741-based distortion circuit, I realised that the LM741 sounds really good when it clips, but the transition out of clipping is really nasty and blatty. I did some research and found that op-amp clipping is at the heart of the Crowther Hotcake, and that this pedal is also known for its blatty decay (as mentioned in this article). I've been trying to think of ways to address this problem, and I'm hoping that you guys might be able to help me.

One idea I've had is to use an overdriven LM741 in the dirty side of a clean/dirty blend circuit. The LM741 would be set up to always clip, entirely avoiding the problem of nasty decay. Expanding on that, there could be a modified compressor circuit which pans between the clean and dirty sides automatically depending on the input's amplitude.

Are these ideas feasible? Is there a better alternative? Or is there just no way to get op-amp clipping without the nasty decay?

[Fancy Lime]

Hi there,

my favorit method for dealing with this in problem is to hide the decay splat behind some additional diode to ground clipping. The trick is to choose the diodes right, so that they clip enough during the decay to mask the splattyness of the opamp, but still let the sound of the opamp clipping shine through when it is hitting its max capibilities. The ProCo Rat does that quite famosly. The Turbo Rat does it better imho, by using Red LEDs as clippers. I would suggest trying different color LEDs, maybe with an additional resistors (1k or so) in series with them. Superbright blue LEDs do it for me but  may leave too much splat in for your taste.

Also try to put a high-cut cap in the feedback loop of the opamp, if there isn't one already. Play with the cap value, starting at 1n or so. That will help with the splat but also kill treble at some point so you have to find your personal sweet spot.

Hope that helps,
Andy

[marcelomd]

The Marshall Guv'nor variants all clip the first opamp. A TL072. I like that sound.
I've read the Klon Centaur does that too. Also a TL072
Tech 21's Bass Driver clips a TL2272, a TL072 with rail-to-rail capabilities.

I traced a distortion from a local brand that is 100% opamp distortion. The sound is awesome, but quite noisy. I'll see if I find the schematic here.

I don't hear splatting in any of them.

[amptramp]

When you are using unspecified characteristics such as op amp clipping, you run the risk that a change in manufacturer or process may not affect the characteristics on the spec sheet but may affect unspecified or loosely specified characteristics such as clipping.  Most op amps have a range or a worst-case spec for operation with inputs or outputs near the power rails but as long as these specifications are not violated, they may be subject to change which may alter the effect in a circuit dependent on clipping.